<template>
  <div>
    <router-link
     tag="div"
     to="/"
     class="header-abs"
     v-show="showAbs"
     >
      <div class="iconfont header-abs-back">&#xe624;</div>
    </router-link>

    <div
     class="header-fixed"
     v-show="!showAbs"
     :style = "opacityStyle"
     >
      <router-link to="/">
        <div class="iconfont header-fixed-back">&#xe624;</div>
      </router-link>
      景点详情
    </div>
  </div>
</template>

<script>
export default {
  name: "DetailHeader",
  data(){
      return{
         showAbs:true,
         opacityStyle:{
           opacity:0
         }
      }
  },
  methods:{
    handleScroll(){
      //  console.log(document.documentElement.scrollTop)
       const top  = document.documentElement.scrollTop
       if(top>60){
         let  opacity = top/140
         opacity = opacity>1? 1:opacity
         this.opacityStyle = {opacity}
         this.showAbs  = false
       }else{
         this.showAbs = true
       }
    }
  },
  activated(){
       window.addEventListener('scroll',this.handleScroll)
  },
  //移除全局监听事件，否则会在其他页面上触发该事件
  deactivated(){
    window.removeEventListener('scroll',this.handleScroll)
  }
};
</script>

<style lang="stylus" scoped>
@import '~styles/varibles.styl'
.header-abs {
  position: absolute;
  left: 0.2rem;
  top: 0.2rem;
  border-radius: 0.4rem;
  background: rgba(0, 0, 0, 0.8);
  height: 0.5rem;
  width: 0.6rem;

  // display flex
  // justify-content center
  // align-items center
  .header-abs-back {
    color: #eee;
    position: relative;
    top: 0.15rem;
    left: 0.15rem;
    font-size: 0.3rem;
  }
}

.header-fixed {
  z-index: 2;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: $headerHeight;
  line-height: $headerHeight;
  text-align: center;
  color: #fff;
  background: $bgColor;
  font-size: 0.32rem;

  .header-fixed-back {
    position: absolute;
    top: 0;
    left: 0;
    width: 0.64rem;
    text-align: center;
    font-size: 0.4rem;
    color: #fff;
  }
}
</style>